JP3883177B2 - Color image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a color image forming apparatus such as an electrophotographic copying machine, a printer, or a facsimile, and in particular, a plurality of color toner images formed by an image process unit are formed on an endless belt-like transfer belt. The present invention relates to a color image forming apparatus which transfers a transfer color image to a transfer medium.
[0002]
[Prior art]
As one type of color image forming apparatus, a transfer color image formed by superimposing a plurality of color toner images formed by an electrophotographic image process unit on an endless belt-like transfer belt is transferred to a transfer medium. There is a method. As a color image forming apparatus of such a system, a structure called a tandem type is typically used.
[0003]
In the color image forming apparatus of the above system represented by the tandem type, the alignment technique between the respective colors is an important issue due to its structure. The following are mainly components for misregistration of each color.
[0004]
Skew, registration deviation in the sub-scanning direction, pitch unevenness in the sub-scanning direction, registration deviation in the main scanning direction, magnification error in the main scanning direction
Various inventions have heretofore been made for such alignment of colors.
[0006]
For example, Japanese Patent Application Laid-Open No. 8-50385 (Patent No. 2858735) detects the positions of a plurality of marks (correction patterns) formed on a transfer moving body (transfer belt), and compares the positions with other colors with respect to a reference color. A technique is disclosed that automatically corrects misalignment between the main scanning direction and the sub-scanning direction.
[0007]
Japanese Laid-Open Patent Publication No. 63-286864 (Japanese Patent No. 2642351) discloses a reference portion composed of a straight line extending in the main scanning direction on an endless conveying means (transfer belt) and an oblique line extending obliquely thereto ( Correction pattern) is formed, and the amount of deviation of the diagonal line in the main scanning direction is calculated from the comparison between the ideal value of the interval between the reference portion and the diagonal line and the actual detection interval, and based on the result, the main scanning writing timing There has been disclosed a technique in which at least one of a clock and a writing clock is corrected, thereby automatically correcting a shift amount of each color in the main scanning direction.
[0008]
[Problems to be solved by the invention]
The user's request for the formation of a color image may differ depending on the time. For example, a high-quality image with high accuracy may be requested while accepting that it takes some time, or a printout in a shorter time may be requested without requiring so much accuracy.
[0009]
In contrast, in color image forming apparatuses, especially color image forming apparatuses that transfer a color image formed by superimposing each color on a transfer belt such as a tandem type onto a transfer medium, even a printout is possible. It takes a lot of time. Under such circumstances, the above-described alignment correction for preventing the color misregistration as described above is a cause of increasing the printing time in a color image forming apparatus using a transfer belt. On the other hand, in a color image forming apparatus using a transfer belt, when high-precision color matching is to be performed, color matching correction is inevitable to prevent misregistration of each color. The more strictly, the higher the quality image can be obtained.
[0010]
That is, there is a trade-off relationship between shortening the printing time and increasing the print quality, and it is difficult to satisfy both. For this reason, there exists a problem that the request | requirement of a different user according to the time as mentioned above cannot be satisfied.
[0011]
An object of the present invention is to satisfy different users' demands from time to time for shortening printing time and improving print quality.
[0012]
[Means for Solving the Problems]
The present invention provides a color image forming apparatus that forms a color image by superimposing a plurality of color toner images formed by an image processing unit, and aligns each color on an image carrier on which the toner image can be formed by the image processing unit. A correction pattern is formed, and an alignment unit that performs an alignment process for each color based on the formed correction pattern is provided, and a first processing mode for the alignment process for each color is provided when instructed by a user. a first mode for processing, have a second mode for automatically performing the different second processing and holds the first processing in accordance with the predetermined condition, the first processing, skew correction Then, a correction pattern is formed for each sequence of main scanning magnification correction, main scanning / sub-scanning registration correction, and based on the detection result of these correction patterns, the correction pattern is formed. In the second processing, a common correction pattern is formed, and a main scanning magnification correction sequence and a main scanning / sub-scanning registration correction sequence are formed based on the detection result of the common correction pattern. Performs alignment processing by .
[0013]
Therefore, it is possible to select an optimum alignment process according to various usage scenes.
[0015]
Such a first mode is selected in a usage scene that requires the positional deviation correction accuracy of each color, thereby improving the positional deviation correction accuracy of each color.
[0019]
Such a second process is selected in a usage scene where the color misregistration correction process for each color is desired to be completed in a short time, thereby reducing the time required for the color misregistration correction process for each color.
[0024]
According to a second aspect of the invention, in the color image forming apparatus according to claim 1, wherein said second mode is executed interrupting during a print job.
[0025]
As a result, the time required for the entire print job including the misregistration correction processing for each color can be shortened.
[0026]
According to a third aspect of the invention, in the color image forming apparatus according to any one of claims 1 to 2, wherein the second mode is performed immediately before the printing operation to be performed in response to a print request.
As a result, the time required for the entire print job including the misregistration correction process for each color can be shortened.
[0027]
According to a fourth aspect of the present invention, in the color image forming apparatus according to the first to third aspects, the first mode is executed in accordance with an instruction from a printer driver.
[0028]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of the present invention will be described with reference to the drawings.
[0029]
This embodiment is an example applied to a tandem type color image forming apparatus.
[0030]
FIG. 1 is a front view of an image processing unit and a transfer belt for explaining an image forming principle of a color image forming apparatus.
[0031]
Image processing sections 1 that form images of different colors (yellow: Y, magenta: M, cyan: C, black: K) are arranged in a line along a transfer belt 3 that conveys a transfer sheet 2 as a transfer medium. Has been. The transfer belt 3 is provided between a driving roller 4 that rotates and a driven roller 5 that rotates and is driven to rotate in the direction of the arrow in FIG. A paper feed tray 6 in which the transfer paper 2 is stored is provided below the transfer belt 3. The transfer sheet 2 at the uppermost position among the transfer sheets 2 stored in the sheet feed tray 6 is fed toward the transfer belt 3 during image formation, and is attracted onto the transfer belt 3 by electrostatic adsorption. The adsorbed transfer paper 2 is conveyed to the first image processing unit 1 (yellow), where yellow image formation is performed.
[0032]
The first image processing unit 1 (yellow) includes a photosensitive drum 7Y and a charger 8Y, an exposure unit 9, a developing unit 10Y, and a photosensitive cleaner 11Y arranged around the photosensitive drum 7Y. . The surface of the photosensitive drum 7Y is uniformly charged by the charger 8Y, and then exposed by the exposure device 9 with the laser light LY corresponding to the yellow image, thereby forming an electrostatic latent image. The formed electrostatic latent image is developed by the developing device 10Y, and a toner image is formed on the photosensitive drum. This toner image is transferred to the transfer paper 2 by the transfer device 12Y at a position (transfer position) where the photosensitive drum 7Y and the transfer paper 2 on the transfer belt 3 are in contact with each other. ) Is formed. In the photoreceptor drum 7Y after the transfer, unnecessary toner remaining on the drum surface is cleaned by the photoreceptor cleaner 11Y to prepare for the next image formation.
[0033]
As described above, the transfer paper 2 on which the single color (yellow) is transferred by the first image processing unit 1 (yellow) is conveyed to the second image processing unit 1 (magenta) by the transfer belt 3. Similarly, the toner image (magenta) formed on the photosensitive drum 7M is transferred onto the transfer paper 2 in a similar manner. The transfer paper 2 is further conveyed in order to the third image processing unit 1 (cyan) and the fourth image processing unit 1 (black), and similarly, the formed toner image is transferred to the transfer paper 2. As a result, a color image is formed on the transfer paper 2. Note that the second to fourth image processing units 1 (magenta, cyan, and black) have the same structure as the first image processing unit 1 (yellow), and a description thereof will be omitted.
[0034]
Then, the transfer paper 2 on which the color image is formed by passing through the fourth image processing unit 1 is peeled off from the transfer belt 3, fixed by the fixing device 13, and then discharged.
[0035]
FIG. 2 is a perspective view of the transfer belt 3 showing a state in which the correction pattern 14 is formed on the transfer belt 3.
[0036]
In the tandem type color image forming apparatus shown in FIG. 1, an alignment technique between colors becomes an important issue because of its configuration. As described above, the components of misregistration of each color mainly include the following.
[0037]
-Skew-Registration deviation in the sub-scanning direction-Pitch unevenness in the sub-scanning direction-Registration deviation in the main scanning direction-Magnification error in the main scanning direction
Therefore, in the color image forming apparatus of the present embodiment, before performing the actual color image forming operation on the transfer paper 2, the color misregistration is corrected. For this purpose, first, a correction pattern 14 for correcting misregistration of each color is formed on the transfer belt 3, and this is detected by two detection sensors 15 and 16. Therefore, in the present embodiment, the two detection sensors 15 and 16 are arranged at both ends of the transfer belt 3 in the main scanning direction, and the transfer belt 3 is corrected in accordance with the arrangement positions of the detection sensors 15 and 16. A pattern 14 is formed. Such a correction pattern 14 is detected when the transfer belt 3 rolls and passes through the detection sensors 15 and 16 in order.
[0039]
In the color image forming apparatus of the present embodiment, when the correction pattern 14 is detected, various shift amounts and correction amounts are calculated from the detection results, and correction of each shift component is performed as follows.
[0040]
FIG. 3 is a block diagram showing an electrical hardware configuration.
[0041]
A configuration and function for processing and setting (correcting) data detected by the detection sensors 15 and 16 will be described based on the block diagram shown in FIG. First, the signals obtained from the detection sensors 15 and 16 are amplified by the AMP 17, pass only the signal component of the line detection by the filter 18, and are converted from analog data to digital data by the A / D converter 19. Data sampling is controlled by the sampling controller 20, and the sampled data is stored in the FIFO memory 21.
[0042]
After detection of one way the correction pattern 14 is completed, data stored in through the I / O port 22, is loaded by a data bus 23 to the CPU24 and RAM 25, processing for calculating the various displacement amount CPU24 To do. Further, the CPU 24 receives fine adjustment amount information of each shift component from an operation panel (not shown) or a printer driver via the I / O port 22 and calculates a final correction amount. This process will be described later.
[0043]
The CPU 24 is a stepping motor (not shown) which is a driving source of the transfer belt 3 in order to execute skew correction, change of the main resist, change of the sub resist, and change of the image frequency based on the magnification error based on the obtained various correction amounts. The drive and write control board 26 is set. The write control board 26 is provided with a device capable of setting the output frequency very finely, for example, a clock generator using a voltage controlled oscillator (VCO) for each color in addition to controlling the main resist and the sub resist. In the color image forming apparatus of the present embodiment, the output is used as an image clock.
[0044]
Further, the CPU 24 monitors the detection signals from the detection sensors 15 and 16 at an appropriate timing, so that the correction pattern 14 can be reliably detected even if the transfer belt 3 and the light emitting portions of the detection sensors 15 and 16 are deteriorated. The light emission amount control unit 27 controls the light emission amount so that it can be detected, so that the level of the light reception signal from the light receiving units of the detection sensors 15 and 16 is always constant.
[0045]
On the other hand, the ROM 28 stores various programs including a program for calculating various deviation amounts. The address bus 29 is used to specify a ROM address, a RAM address, and various input / output devices.
[0046]
Here, various shift amounts and correction amount calculations based on the detection result of the correction pattern 14 in the color image forming apparatus of the present embodiment, and methods for correcting each shift component will be described.
[0047]
First, correction of skew deviation will be described. The skew deviation is corrected by changing the inclination of a mirror (not shown) for turning back the laser beams of the respective colors in the exposure unit 9. For example, a stepping motor is used as a drive source for biasing the mirror to change the tilt of the mirror.
[0048]
Next, correction of the writing timing in the sub-scanning direction will be described with reference to the timing chart of FIG. FIG. 4 is a timing chart showing the timing of various signals when correcting the writing start timing in the sub-scanning direction. In this case, it is assumed that the correction resolution is 1 dot.
[0049]
As shown in FIG. 4, the image area signal (write enable signal) in the sub-scanning direction is adjusted for writing at the timing of the synchronization detection signal. As a result of detecting the correction pattern 14 and performing a predetermined calculation, if it is desired to advance the 1-dot write start position, the write enable signal may be activated earlier by one synchronization detection signal as shown in FIG.
[0050]
Next, correction of the writing timing in the main scanning direction will be described with reference to the timing chart of FIG. FIG. 5 is a timing chart showing the timing of various signals when correcting the writing start timing in the main scanning direction. In this case, it is assumed that the correction resolution is 1 dot.
[0051]
First, the image writing clock is obtained in such a manner that a clock in which each line is accurately in phase is obtained by the falling edge of the synchronization detection signal. Image writing is performed in synchronization with this clock signal, but an image writing enable signal in the main scanning direction is also generated in synchronization with this clock. Now, as a result of detecting the correction pattern 14 and performing a predetermined calculation, if it is desired to advance the 1-dot write start position, the write enable signal may be activated earlier by 1 clock as shown in FIG.
[0052]
Next, magnification correction in the main scanning direction will be described with reference to FIG. As a result of detecting the correction pattern 14 and performing a predetermined calculation, when the magnification in the main scanning direction is deviated from the reference color (one color in the correction pattern), a device that can change the frequency in a very small step, for example, The magnification can be changed by using a clock generator or the like.
[0053]
As described above, in the color image forming apparatus of the present embodiment, skew deviation, sub-scan direction write timing correction, main scan direction write timing correction, and main scan direction magnification correction are executed. Such various color registration corrections are based on arithmetic processing of the CPU 24 according to a program for calculating various displacement amounts stored in the ROM 28 and driving and controlling each driven object such as the image processing unit 1. Executed.
[0054]
The color image forming apparatus of the present embodiment has a plurality of execution modes as processing modes for alignment correction for preventing such color misregistration, and each execution mode is selected by the user. It is possible. That is, in the color image forming apparatus of the present embodiment, the alignment process for each color is inevitable in order to prevent the misregistration of each color, but it takes some time to perform the alignment correction for that purpose. Usually, the correction accuracy and the execution time are in a trade-off relationship. Therefore, in the present embodiment, in consideration of different user needs depending on the occasion, a plurality of correction execution modes are prepared, and each color is aligned in an optimal execution mode in various usage situations. Therefore, the user satisfaction is improved.
[0055]
In the color image forming apparatus of the present embodiment, first, as a first mode, a mode in which correction accuracy is emphasized is provided. In this mode, a correction pattern 14 is formed on the transfer belt 3, the correction pattern 14 is recognized according to the outputs of the detection sensors 15, 16, a correction value is calculated based on the recognition result, and the correction value is This is an alignment process of each color for driving and controlling a driven object such as the image process unit 1, that is, a process of performing each operation of forming, detecting, calculating, and correcting the correction pattern 14 a plurality of times.
[0056]
FIG. 6 is a flowchart showing the flow of the alignment correction process for each color in the first mode.
[0057]
In the first mode, first, a correction pattern 14 for skew correction is formed (step S101). Then, the correction pattern 14 is recognized based on the outputs of the detection sensors 15 and 16 that detect the correction pattern 14 (step S102), and the skew correction amount is calculated based on the recognition result (step S103). Skew correction is executed (step S104). As described above, the skew correction is performed by changing the inclination of a mirror (not shown) for returning the laser beams of the respective colors in the exposure unit 9. That is, the CPU 24 is executed by outputting a signal for driving and controlling, for example, a stepping motor that energizes such a mirror.
[0058]
Next, a correction pattern 14 for correcting the main scanning magnification is formed (step S105). The correction pattern 14 is recognized based on the outputs of the detection sensors 15 and 16 that detect the correction pattern 14 (step S106), and the main scanning magnification correction amount is calculated based on the recognition result (step S107). Thereafter, main scanning magnification correction is executed (step S108).
[0059]
Next, a correction pattern 14 for main / sub resist correction is formed (step S109). Then, the correction pattern 14 is recognized based on the outputs of the detection sensors 15 and 16 that detect the correction pattern 14 (step S110), and the main / sub resist correction amount is calculated based on the recognition result (step S111). After that, main / sub resist correction is executed (step S112).
[0060]
As described above, in the first mode, the operations of forming, detecting, calculating, and correcting the correction pattern 14 are performed a plurality of times. When the skew is corrected, the main scanning magnification and the main / sub-registration are also shifted. This is because when the scanning magnification is corrected, the main scanning resist also shifts. Therefore, the order (sequence) for correcting the shift component is also important. As a result of executing the alignment correction of each color in the order (sequence) as described above, the correction accuracy is improved and the image quality is improved. To do.
[0061]
Such a first mode is performed, for example, when the user gives an instruction to execute alignment from the printer driver or the operation panel.
[0062]
The color image forming apparatus according to the present embodiment includes a color matching execution mode for each color that places importance on shortening the execution time as the second mode. This execution mode has fewer correction pattern formations, detections, calculations, and corrections than the first mode described above.
[0063]
FIG. 7 is a flowchart showing the flow of the alignment correction process for each color in the second mode.
[0064]
In the second mode, first, a correction pattern 14 for main scanning magnification and main / sub resist correction is formed (step S201). The correction pattern 14 is recognized based on the outputs of the detection sensors 15 and 16 that detect the correction pattern 14 (step S202), and the main scanning magnification correction amount is calculated based on the recognition result (step S203). A main / sub registration correction amount is calculated (step S203), main scanning magnification correction is executed (step S205), and main / sub registration correction is executed (step S206). In this case, the order in which step S203 and step S204 are executed may be reversed, and the order in which step S205 and step S206 are executed may be reversed.
[0065]
Since the skew deviation amount has a characteristic that is not noticeable on the image as a deviation component, skew correction is not performed in the second mode.
[0066]
In the present embodiment, the main scanning magnification correction and the main scanning registration correction are performed based only on the recognition result of one correction pattern 14. However, as described above, if the main scanning magnification is corrected, the main scanning registration is also shifted. Therefore, if the main scanning magnification correction and the main scanning registration correction are performed as they are, the alignment correction amount is shifted. End up. Therefore, in the present embodiment, the main scanning registration deviation amount that occurs when the main scanning magnification is changed is predicted and corrected together with the actual main scanning registration deviation amount calculated from the detection result.
[0067]
Such a second mode is executed when positioning is performed by interrupting the print job.
[0068]
The second mode is also executed when each color is aligned immediately before printing when printing is requested, and printing is permitted after the positions of each color are aligned.
[0069]
In such a case, the second mode is effective because there is a request to shorten the time required for alignment of each color as much as possible.
[0070]
【The invention's effect】
According to the present invention , the user can select an optimal alignment process according to various usage scenes.
[0071]
Since the present invention has the first mode as one of the execution modes, it is possible to improve the misregistration correction accuracy of each color by selecting the first mode in the usage scene where the misregistration correction accuracy of each color is required. Therefore, it is possible to contribute to realization of high image quality.
[0072]
In the first process, a correction pattern is formed for each sequence of skew correction, main scanning magnification correction, main scanning / sub-scanning resist correction, and alignment processing by each sequence is performed based on the detection result of these correction patterns. Do. As described above, since a correction pattern is formed for each sequence to perform positional deviation correction, it is possible to improve the positional deviation correction accuracy of each color, and thus contribute to the realization of higher image quality.
[0073]
In the second process, a common correction pattern is formed, and based on the detection result of the common correction pattern, the alignment process is performed by the main scanning magnification correction sequence and the main scanning / sub-scanning registration correction sequence. The time required can be shortened, and therefore the waiting time of the user can be shortened.
[0076]
Before Stories second mode, since it is executed interrupting during a print job, it is possible to shorten the time required for the entire print job including the positional deviation correcting process for each color, thus, the waiting time of the user It can be shortened.
[0077]
Before Stories second mode, since it is executed immediately before the printing operation to be performed in response to a print request, it is possible to shorten the time required for the entire print job including the positional deviation correcting process for each color, thus The waiting time of the user can be shortened.
[Brief description of the drawings]
FIG. 1 is a front view of an image processing unit and a transfer belt for explaining an image forming principle of a color image forming apparatus showing an embodiment of the invention.
FIG. 2 is a perspective view of the transfer belt showing a state in which a correction pattern is formed on the transfer belt.
FIG. 3 is a block diagram showing an electrical hardware configuration.
FIG. 4 is a timing chart showing timings of various signals when correcting the writing start timing in the sub-scanning direction.
FIG. 5 is a timing chart showing timings of various signals when correcting the writing start timing in the main scanning direction.
FIG. 6 is a flowchart showing a flow of alignment correction processing for each color in the first mode.
FIG. 7 is a flowchart showing a flow of alignment correction processing for each color in the second mode.
[Explanation of symbols]
1 Image process part 2 Transfer media (transfer paper)
3 Transfer belt 14 Correction patterns 15 and 16 Detection sensor

Claims (4)

In a color image forming apparatus that forms a color image by superimposing a plurality of color toner images formed by an image processing unit,
The image processing unit includes an alignment unit that forms a correction pattern for alignment of each color on an image carrier on which a toner image can be formed, and performs an alignment process for each color based on the formed correction pattern,
As the processing mode of the alignment processing for each color, a first mode in which the first processing is performed when instructed by the user, and a second processing that is different from the first processing when a predetermined condition is satisfied are automatically performed. have a second mode in which the manner,
In the first process, a correction pattern is formed for each sequence of skew correction, main scanning magnification correction, main scanning / sub-scanning resist correction, and alignment processing by each sequence is performed based on the detection result of these correction patterns. Done
In the second process, a common correction pattern is formed, and based on the detection result of the common correction pattern, an alignment process using a main scanning magnification correction sequence and a main scanning / sub-scanning registration correction sequence is performed. Color image forming apparatus. The color image forming apparatus according to claim 1, wherein the second mode is executed by interrupting a print job . The second mode, the color image forming apparatus according to 2 or claims 1, characterized in that it is performed immediately before the printing operation to be performed in response to a print request. 4. The color image forming apparatus according to claim 1 , wherein the first mode is executed in accordance with an instruction from a printer driver .

Images